It is a well established practice in underground mining work, such as coal mining, tunnel excavation, or the like, to reinforce the roof of the mine to prevent its collapse. There are various types of reinforcement apparatus, the most common are of the mining bolt type. These mining bolts are of various designs.
A problem exists with conventional mining bolts in that after installation, conventional mining bolts will often tear loose or shear due to blasts or natural rock shifts. This could lead to a catastrophe such as a cave-in. Accordingly, several attempts have been made in the prior art to produce a mining bolt that resists shear.
Split-Set.RTM. by Ingersoll-Rand is a mining bolt which is comprised of a c-shaped metal member which is forced into a bore hole and supports the rock by friction. The hollow shape of the Split-Set.RTM. bolt allows the bolt to deform rather than break when a rock shift occurs. Unfortunately, the c-shape is not a conventional shape and thus is costly to manufacture.
Swellex.RTM. by Atlas Copco, Inc. of Sweden is a hollow folded c-shaped tube which expands in the bore hole by means of high pressure water. During the swelling process, the Swellex.RTM. bolt adapts to fit the irregularities of the bore hole. The hollow shape allows the tube to deform during rock shifts. Unfortunately, the complex shape of the Swellex.RTM. mining bolt is expensive to manufacture. Further, the necessary high pressure water tools and fittings add to the expense and complexity of the method.
Spin-Lock.RTM. by Williams Co. discloses a rock bolt which has a hollow interior and has open ends for allowing grout to be pumped therethrough. No resin cartridges are disclosed.
The present invention describes a mining bolt which can be made from inexpensive, stock round tubing. The hollow interior of the tubing allows the mining bolt of the present invention to deform during rock shifts instead of break. Further, the hollow mining bolt of the present invention saves steel as compared with a solid mining bolt of equal strength.